<i>OsMADS25</i> regulates root system development via auxin signalling in rice

Abstract

Summary The phytohormone auxin is essential for root development in plants. Os MADS 25 is a homologue of the AGL 17 ‐clade MADS ‐box genes in rice. Despite recent progress, the molecular mechanisms underlying the regulation of root development by Os MADS 25 are not well known. It is unclear whether Os MADS 25 regulates root development via auxin signalling. In this study, we examined the role of Os MADS 25 in root development and characterized the signalling pathway through which Os MADS 25 regulates root system development in rice. Os MADS 25 overexpression significantly increased, but RNA i gene silencing repressed primary root ( PR ) length and lateral root ( LR ) density. Moreover, Os MADS 25 promoted LR development in response to NO 3 − . Further study showed that Os MADS 25 increased auxin accumulation in the root system by enhancing auxin biosynthesis and transport, while also reducing auxin degradation, therefore stimulating root development. More importantly, Os MADS 25 was found to regulate Os IAA 14 expression directly by binding to the CA rG‐box in the promoter region of Os IAA 14 , which encodes an Aux/indole acetic acid ( IAA ) transcriptional repressor of auxin signalling. Elevated auxin levels and decreased Os IAA 14 expression might lead to reduced Os IAA 14 protein accumulation, as a mechanism to regulate auxin signalling. Therefore, our findings reveal a molecular mechanism by which Os MADS 25 modulates root system growth and development in rice, at least partilly, via Aux/ IAA ‐based auxin signalling.